1. Field of the Invention
This invention relates to a cable with a ripcord, and a method for stripping an intermediate part of the cable.
2. Description of the Related Art
To remove the plastic sheath of a cable having a plastic sheath covering a cable core, first, a circumferential preparatory slit is made in the plastic sheath with a knife or the like at the end of the part to be removed. Then, one or two preparatory slits are made with a knife or the like in the longitudinal direction in the part of plastic sheath to be removed. These preparatory slits are then split open, and the plastic sheath is peeled off.
However, when making preparatory slits in a plastic sheath in the circumferential and longitudinal directions in this manner, great care is needed to avoid damage the cable core inside, and the work requires practice and skill.
Because of this, an alternative special tool for forming circumferential and longitudinal-direction preparatory slits has also been used to avoid damaging the cable core. However, different sizes of cable and different thicknesses and external diameters of sheaths and so on, require numerous different tools to be prepared, and the mechanism of the tool has been complicated.
A method has also been practiced wherein, to facilitate the removal the plastic sheath, a ripcord made, for example, of a tensile fiber is provided inside the plastic sheath in the longitudinal direction of the cable core, and the plastic sheath is removed using this ripcord.
In this method, the plastic sheath is split open in the longitudinal direction by pulling alongside the cable, an end of the ripcord extracted from an end of the cable back, and this split part of the plastic sheath is then cut off.
Thus, in this cable with a ripcord at an end, it is possible to strip off the plastic sheath easily, because an end of the ripcord can be extracted easily.
However, it is not easy to extract an end of the ripcord, at an intermediate part of the cable. This is because the location of the ripcord is not visible from the surface of the plastic sheath.
To extract the ripcord at an intermediate part of the cable, it is necessary to make a circumferential preparatory slit in the plastic sheath with a knife or the like and then locate and extract the ripcord.
Thus this case which also requires the operation of making a circumferential preparatory slit in the plastic sheath, requires great care and skill as well so as not to damage the cable core.
It is therefore an object of the present invention to provide a cable and a stripping method with which the cable can be stripped easily without damaging the cable core even at an intermediate part of the cable.
The cable of this invention is a cable having a plastic sheath provided on a cable core; a groove extending in the longitudinal direction of the cable is formed in the inner surface of the plastic sheath, a ripcord is fitted in the groove, and a position-indicating means showing the position of the ripcord is provided on the outer surface of the plastic sheath in which the ripcord is fitted.
Alternatively, instead of providing the groove in the inner surface of the plastic sheath and inserting the ripcord into the groove, the ripcord can be fixed to the inner surface of the plastic sheath by direct adhesion and then a position-indicating means showing the position of the ripcord can be provided on the outer surface of the plastic sheath at the point where the ripcord is adhered.
A cable having a ripcord according to the invention can also be a self-supporting cable.
In a self-supporting cable, the cable is comprised of a supporting wire and a cable core, each covered with a plastic sheath, and the plastic sheath covering the supporting wire and the plastic sheath covering the cable core are connected to each other by plastic neck parts located intermittently in the longitudinal direction of the cable; also, on the side of the cable core plastic sheath nearest the supporting wire and the farthest side thereof from the supporting wire, a tensile member extending in the longitudinal direction is embedded in the sheath resin, respectively.
As a method of applying the invention to this kind of self-supporting cable, for example, in two locations of the plastic sheath, each 90xc2x0 apart in the circumferential direction from the positions where the tensile members are embedded, either grooves extending in the longitudinal direction of the cable are provided in the inner surface of the plastic sheath and ripcords are fitted in the grooves, or ripcords are directly adhered to the inner surface of the plastic sheath, and a position-indicating means showing the positions of the ripcords are provided on the outer surface of the plastic sheath at the points where the ripcords are fitted or adhered.
When this is done, the operation of stripping an intermediate part of the self-supporting cable, facilitate the removal of the plastic sheath without damaging the cable core. And of course, the fundamental characteristics of the self-supporting cable are maintained. That is, because this self-supporting cable can tolerate wind pressures when used as an aerial cable, and also the cable core can be made to have surplus length, excessive tension does not act undesirably on the cable core and the cable is suitable as an optical fiber cable for subscriber line use.
In the case of the cable having on the outer surface of the plastic sheath a position-indicating means showing the position of the ripcords as described above, after the cable is installed, by cutting a part of the plastic sheath with a knife or the like at any intermediate position on the cable using the position-indicating means as a guide and then pulling the ripcords in the direction in which the plastic sheath is to be split, the plastic sheath can be split in the longitudinal direction of the cable, and this split part can then be cut off to expose the cable core. By means of this procedure even an intermediate part of the cable can be stripped easily, and thus simplifies intermediate branching work.